This is fantasy, I am not a prepper or a doomsday thinker.
An electromagnetic pulse (commonly abbreviated EMP) just hit the USA.
After a few days
Money is worthless
Grocery Stores are empty and Looted
Electricity , Cell Phones and Water is off
Rioting in the streets.

I'm far more concerned about the biological effects of non ionizing electromagnetic radiation. Than procuring a meal or two

From what I've read... If an EMP was going to be detonated, it would be done above the atmosphere in order to have a wider area of affect. Two or three would take out the eastern seaboard if placed correctly.

However, I see your point if it was detonated on the ground or a few thousand feet up. I don't think we'd worry too much since we'd probably be toast.

Another concern would be the EMP effecting the earths magnetic fields. It's been speculated that the axis and rotation might actually be affected.
That would cause some super cereal issues.

That speculation is pretty much false since the sun has released massive emp fields that would 100% present the situation the OP states. Depending on how massive the emp was would change how long the power would be out. Was the blast big enough to destroy the transformers or just shut them down?